Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

668
FXUS63 KLOT 052324
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
624 PM CDT Sun Jul 5 2026

.KEY MESSAGES...

- Isolated to widely scattered showers and thunderstorms are
  possible (20-40% chance) this afternoon mainly near/south of
  I-80, but most areas will remain dry.

- Drier and more seasonable conditions are expected to start
  the week before stormier weather returns late week.

&&

.DISCUSSION...
Issued at 152 PM CDT Sun Jul 5 2026

Early this afternoon, we`re finding a cluster of light to
moderate showers stirring over the lake. This cluster was
brought on by a vort lobe spinning over the southern end of the
lake about the back end of the departing trough. Notably weak
convective layer shear isn`t helping move these showers along
very well as they track toward the south at near or less than 10
mph. Latest radar trends suggest that this activity should
target portions of northwest Indiana within the next couple of
hours. However, the southern extent of the showers has been
fizzling away as of late and they may even fail to survive to
the shore.

Coverage of isolated to widely scattered showers is anticipated
to blossom and spread inland away from the lake as we progress
through the afternoon, especially near and south of I-80. The
greatest forcing tied to this vort will focus over the southern
half of the CWA and a northeasterly low level wind field will
continue to spread cooler, more stable low level air inland from
the lake. Meanwhile, instability continues to build across
outlying areas with several hundred to around 1,000 Joules of
largely uncapped MLCAPE south of I- 80 and especially south of
the Kankakee River expected for the mid-late afternoon. Latest
CAM guidance generally favors areas near/south of the Kankakee
River during the latter half of the afternoon and into early
evening for the highest (still widely scattered) precip
coverage. A handful of thunderstorms will be possible down in
these parts as well. The limited instability and weak shear will
inhibit a severe threat. However, the plentiful moisture, poor
shear, and limited forcing beyond the low levels could make for
slow-moving low-echo centroid pockets of heavy rainfall. Should
a heavier shower or storm linger over an area that saw lots of
rain or any flooding over the past few days, minor flooding
impacts could be reinvigorated, although this is a low and
isolated potential.

Farther north up into the Chicago metro and west of the
lakeshore, the environment appears most supportive of precip as
of this writing during the early part of the afternoon than
later in the day. The footprint of the vort looks to spread
inland carrying the better large scale forcing farther south for
the mid-late afternoon. An isolated thunderstorm can`t be ruled
out north of I-80, but the odds are best prior to 3-4 PM.
Additionally, a secondary vort ejecting east out of Iowa may
help churn some additional shower activity farther west out
toward I-39 where a handful of CAMs are resolving isolated
pockets, mainly during the latter part of the day. Latest
satellite trends show no distinct signs of new development
anywhere around the area so it may end up being more of a late
afternoon show, which adds confidence to there being little to
no impacts north of I-80. Whatever precip coverage does
materialize should wrap up by mid-evening as the trough axis
moves across stripping forcing and moisture from the area.

Broad, relative high pressure behind the departing system will
bring dry and mostly sunny conditions to Monday and Tuesday.
Highs are forecast in the lower 80s for Monday and mid 80s on
Tuesday. Onshore winds both days, however, will bring noticeably
cooler conditions to locales near the lake with afternoon temps
forecast in the lower and middle 70s around the lakeshore. The
vort lobe from today will get hung up across central IL and
central IN tomorrow and a handful of camps resolve pockets of
daytime showers and thunderstorms similar to today but confined
to our far southeastern CWA, if not outside of the CWA entirely.
Couldn`t argue with the NBM wanting to introduce some slight
chances for storm or two down there tomorrow. Mid-summer heat
will remain through the middle of the week with another synoptic
system favored to traverse the region during the mid-late week
period bringing additional opportunities for rain and
thunderstorms.

Doom

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 623 PM CDT Sun Jul 5 2026

Key Aviation Messages for the current TAF period:

- Showers and storms around and west of the Rockford Metro
  through sunset

- Lingering MVFR cigs for Chicago terminals with low confidence
  on exact timing for improvement to VFR

Lingering showers and storms along a confluence axis are
persisting around KRFD. However, the lightning activity is
already trending downward. Maintained VCSH for an hour, but
drier conditions are slowly developing.

The main impact to the Chicago terminals are the low MVFR cigs.
With little change to the overall weather pattern, it is
understandable why a few models suggest MVFR cigs lingering into
tomorrow morning providing lower confidence in improvement to
VFR cigs. And yet, most models continue to suggest improvement
and a gap in the cloud cover over Lake Michigan has developed
and moving toward Chicago under the influence of the onshore
flow. Outgoing TAFs will show improvement to VFR at 03z, but
will reassess to see if MVFR needs to be extended further into
the overnight.

Winds are expected to remain out of the northeast through the
current TAF period. Speeds will diminish after sunset through
the overnight before picking up again to around 10 knots
tomorrow morning. Isolated gusts 15 to 20 knots are possible
tomorrow morning, but not a signal for them to be frequent
enough for mention in the TAF.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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